JP3349308B2 - Photovoltaic element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates are those concerning the photovoltaic element such as a solar cell, photovoltaic element having a heterojunction constituted by particular combination of a crystalline semiconductor and the amorphous semiconductor it relates to.

[0002]

2. Description of the Related Art In recent years, solar cells using crystalline silicon such as monocrystalline silicon and polycrystalline silicon as photovoltaic elements have been actively researched and put to practical use. Above all, a solar cell having a heterojunction formed by combining amorphous silicon and crystalline silicon can form the junction by a low-temperature process of 200 ° C. or lower and achieve high conversion efficiency. Because of that, it is attracting attention.

Further, it is known that the characteristics of a solar cell are particularly improved by inserting thin intrinsic amorphous silicon into a heterojunction interface between crystalline silicon and amorphous silicon.

On the other hand, in the production of a conventional photovoltaic device combining an amorphous semiconductor and crystalline silicon, unlike a photovoltaic device consisting of only crystalline silicon, a junction is formed on a crystalline silicon substrate. It is necessary to form an amorphous silicon layer and a conductive thin film for this purpose.

Here, conventionally, when these films are formed on a substrate, a manufacturing method such as a plasma CVD method, a sputtering method, or a vapor deposition method is used. In this case, there is a problem that the wraparound occurs not only on the front surface but also on the side surface or the back surface, and a short circuit of the element occurs through these.

Therefore, conventionally, as shown in, for example, "Solar Energy Engineering" (Baifukan, p. 221) and "Challenge to Solar Energy" (Seifunsha, p. The formation of the film while covering the portion prevents the above-mentioned wraparound of the film on the side surface or the back surface.

FIG. 8 is a sectional view showing an example of the structure of a photovoltaic element manufactured by a conventional method using such a mask.

Referring to FIG. 8, this photovoltaic element has n
On the surface of the crystalline silicon substrate 7, an intrinsic amorphous silicon layer 8, a p-type amorphous silicon layer 9, a conductive thin film 3 and a collecting electrode 4 are sequentially formed. The intrinsic amorphous silicon layer 8, the n-type amorphous silicon layer 10, the conductive thin film 3, and the back electrode 5 were sequentially formed.

[0009]

However, in the conventional photovoltaic device shown in FIG. 8, the amorphous silicon layers 9, 10 and the conductive thin film 3 are not formed on the peripheral portion A of the substrate 1. This portion A becomes a non-power generation layer or a high resistance layer and becomes a loss portion. As a result, there is a problem that the effective area is reduced and the conversion efficiency is reduced.

Further, since the conductive thin film 3 also plays a role as an antireflection film, the conductive thin film 3
When a portion where no is formed is formed, there is a problem that reflection loss occurs and light confinement performance is reduced.

On the other hand, in general, when industrial production is considered, it is preferable that the number of steps using a mask is small.
Such a manufacturing method that frequently uses a mask has a problem that mass productivity is poor.

An object of the present invention is to provide a photovoltaic element which solves the above-mentioned problems and has improved conversion efficiency and optical confinement performance, and a method of manufacturing these elements excellent in mass productivity.

[0013]

A photovoltaic device according to the present invention comprises a first conductive type crystalline semiconductor substrate .
Other conductivity type formed by turning up from the surface to the side of the substrate
Laminate comprising an amorphous semiconductor layer and a conductive thin film
From the second main surface of the crystalline semiconductor to the side surface of the substrate
Amorphous semiconductor layer of the same conductivity type formed by wraparound and conductivity
A second stack of a thin film, a photovoltaic element comprising a between the amorphous semiconductor layer of the substrate and the other conductivity type
And an intrinsic amorphous semiconductor layer on the first main surface of the substrate.
The first laminated body is removed at the peripheral portion of
It is characterized in that a groove reaching the body layer is formed.

[0014] Photovoltaic devices according to the invention of claim 2 is one
From the first main surface of the conductive type crystalline semiconductor substrate to the substrate side
Amorphous semiconductor layer of other conductivity type formed by wrapping around the surface
Laminate comprising a conductive layer and a conductive thin film, and a crystalline semiconductor
From the second main surface to the side surface of the substrate.
Composed of an amorphous semiconductor layer of the same conductivity type and a conductive thin film.
A photovoltaic device comprising:
Intrinsic amorphous semiconductor layer between the same conductivity type amorphous semiconductor layer
And a second peripheral surface on the second main surface of the substrate.
The groove reaching the intrinsic amorphous semiconductor layer by removing the stacked body of
It is characterized by being formed .

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

In the photovoltaic device according to the present invention, a groove from which the laminate is removed is formed at the periphery of the laminate comprising the amorphous semiconductor layer and the conductive thin film formed on the crystalline semiconductor substrate.

As a result, leakage current due to the incorporation of the conductive thin film or the amorphous semiconductor layer is eliminated, so that a short circuit at the junction is prevented.

Here, the depth of the groove may be at least a depth to reach the intrinsic amorphous semiconductor layer. This is because the intrinsic amorphous semiconductor layer has a high resistance, so that a short circuit does not occur even if the wraparound portion is not necessarily removed.

In the present invention, the formation of the groove can be performed by, for example, laser irradiation. In the case of cutting removal by laser irradiation, the cutting width is 100 to 20
It can be obtained up to 0 μm. As a result, the effective area is increased, the conversion efficiency can be improved, and the light confinement performance can be improved.

As a method of removing a film using a laser, for example, Japanese Patent Application Laid-Open No. 60-260392 discloses a technique for removing a conductive film, and US Pat. No. 4,824,488 discloses a technique for removing an amorphous semiconductor layer. I have. However, all of these techniques use a laser for forming a junction of an integrated solar cell.

On the other hand, according to the present invention, a laser is used to separate the front and back surfaces of the solar cell, thereby greatly improving the characteristics of the solar cell.

Further, according to the present invention, it is not necessary to use a mask in a manufacturing process, which leads to improvement in mass productivity.

[0029]

[0030]

According to the present invention, it is not necessary to use a mask in the manufacturing process, and it is possible to irradiate a plurality of crystalline semiconductor substrates at once with a laser. There is.

[0032]

【Example】

(Embodiment 1) FIG. 1 is a sectional view showing a manufacturing process of an example of a photovoltaic device according to the present invention.

Hereinafter, a method of manufacturing an example of a photovoltaic device according to the present invention will be described with reference to FIG.

First, as a crystalline semiconductor substrate, the resistivity is 0.1 to 10 Ωcm, the size is 10 cm square, and the thickness is 20 mm.
Using an n-type single crystal silicon substrate 7 of 0 to 400 μm,
Installed without using a mask in plasma CVD equipment,
After evacuating the inside of the apparatus, the apparatus was heated to about 120 to 270 ° C. Next, a glow discharge is generated in the above-mentioned plasma CVD apparatus, and a silicon compound gas such as silane is decomposed by the energy of the plasma, and the intrinsic amorphous silicon layer 8 having a temperature of 250 ° or less is formed on the above-mentioned n-type single crystal silicon. It was formed on the first main surface of the substrate 7. Subsequently, a p-type amorphous silicon layer 9 having a conductivity type different from that of the single crystal silicon substrate 7 is formed on the formed intrinsic amorphous silicon layer 8 by a plasma CVD method in the same manner as the intrinsic amorphous silicon layer 8. Formed by As the reaction gas, the aforementioned silicon compound gas to which diborane gas was added was used.

Next, an intrinsic amorphous silicon layer 8 is formed on a second main surface of the n-type single-crystal silicon substrate 7 opposite to the first main surface, and an n-type impurity is excessively formed thereon. A doped n-type amorphous silicon layer 10 was formed. As the n-type reaction gas, the aforementioned silicon compound gas to which a phosphine gas was added was used.

Table 1 shows the conditions for forming the amorphous silicon layer. In Table 1, “p-type” means the p-type amorphous semiconductor layer 9.
And “n-type” means that the n-type amorphous semiconductor layer 10 is an “i-type”
Indicates the intrinsic amorphous semiconductor layer 8. Also, B ₂
H ₆ and PH ₃ are diluted to 1% by H ₂ gas.

[0037]

[Table 1]

Next, the photovoltaic element is formed on both main surfaces of the n-type single crystal silicon substrate 7 in order to reduce the sheet resistance, prevent reflection, effect light confinement, or prevent alloying of amorphous silicon. On the p-type amorphous silicon layer 9 and the n-type amorphous silicon layer 10, a light-transmitting conductive thin film 3 such as an ITO (Indium Tin Oxide) film was formed by a sputtering method.

Finally, the first of the n-type single crystal silicon
A metal electrode 4 is formed as a collecting electrode on the conductive thin film 3 formed on the main surface side of the substrate, and a metal electrode 5 is formed as a back electrode on the conductive thin film 3 formed on the second main surface side. Then, the film formation process of the photovoltaic element was completed.

FIG. 1A is a sectional view showing the state of the photovoltaic element after the completion of the film forming process. Referring to FIG. 1A, in the above-described entire film forming process, a mask is not used as in the related art, and the film is formed using a method such as a plasma CVD method or a sputtering method. At this stage, the intrinsic amorphous silicon layer 8, the p-type amorphous silicon layer 9, and the conductive thin film 3 formed on the first main surface of the n-type single crystal silicon substrate 7 7 is formed up to the side surface or the second main surface side. On the other hand, the intrinsic amorphous silicon layer 8, the n-type amorphous silicon layer 10 and the conductive thin film 3 formed on the second main surface of the n-type single crystal silicon substrate 7 It is formed up to the side surface or the first main surface side.

Therefore, in this state, the photovoltaic element may be short-circuited and its characteristics may be deteriorated due to the incorporation of these amorphous silicon layers or conductive thin films.

Therefore, in the first embodiment, in order to prevent a short circuit and a deterioration in characteristics, a laser irradiation is performed to laminate the intrinsic amorphous silicon layer 8, the p-type amorphous silicon layer 9, and the conductive thin film 3. A groove 1 was formed in a peripheral portion of the body on the first main surface of the n-type single-crystal silicon substrate 7.

FIG. 1B is a sectional view showing the structure of an example of the photovoltaic element in which the groove 1 is formed as described above.

Referring to FIG. 1B, the depth of the groove 1 is determined by removing at least the stacked body composed of the p-type amorphous silicon layer 9 and the conductive thin film 3, and removing the intrinsic amorphous silicon layer 8. It is only necessary to reach until. That is, since the conductivity of intrinsic amorphous silicon is three orders of magnitude lower than that of p-type amorphous silicon and has high resistance, the intrinsic amorphous silicon layer 8 does not necessarily need to be removed by laser irradiation.

FIG. 2 is a perspective view for explaining the formation state of the groove in the photovoltaic element shown in FIG.

Referring to FIG. 2, in this photovoltaic element, a continuous groove 1 is formed in a peripheral portion of a laminated body formed on a substrate.

The conditions for laser irradiation for forming such grooves are, for example, a laser having a wavelength of more than 400 nm, such as an Ar laser or a second harmonic of a YAG laser, of 0.1 to 10 Joule / cm ² . By using an appropriate power, the laser light can be applied to the conductive thin film 3 and p.
Intrinsic amorphous silicon layer 8 penetrating the amorphous silicon layer 9
To reach. As a result, the conductive thin film 3 and the p-type amorphous silicon layer 9 can be removed. The width of the p-type amorphous silicon layer 9 and the conductive thin film 3 removed by laser irradiation under such conditions is 100 μm to 1 mm.
It was about.

The conversion efficiency of the photovoltaic device of Example 1 (indicated as “the present invention” in Table 2) thus manufactured was measured.

Also, For comparison, a photovoltaic device manufactured using the conventional mask shown in FIG.
) Were measured for conversion efficiency.

Table 2 shows the results.

[0051]

[Table 2]

As is clear from Table 2, according to the present invention, a film can be formed on the entire main surface of the single crystal silicon substrate 7, so that the effective area is increased and the conductivity is increased. It can be seen that the conversion efficiency is improved by about 1% since the entire surface is AR-coated with the thin film.

Embodiment 2 FIG. 3 is a sectional view showing the structure of another example of the photovoltaic device according to the present invention.

Referring to FIG. 3, this photovoltaic element has n
On the second main surface of type single crystal silicon substrate 7, n-type amorphous silicon layer 10 is directly formed without an intervening intrinsic amorphous silicon layer. The other configuration is completely the same as that of the first embodiment shown in FIG.
The description is omitted.

The present invention can be applied to a photovoltaic element in which the intrinsic amorphous silicon layer 8 is formed only on the first main surface side of the n-type single crystal silicon substrate 7 as described above.

A single crystal silicon substrate 7 having only the back surface electrode 5 formed on the second main surface has the same effect.

[0057]

(Embodiment 3) FIG. 4 is a sectional view showing the structure of still another example of a photovoltaic device according to the present invention.

Referring to FIG. 4, in this photovoltaic element, groove 11 is formed not on the first main surface side of n-type single crystal silicon substrate 7 but on the second main surface side. That is, in the third embodiment, the intrinsic amorphous silicon layer 8 and the n-type amorphous silicon layer 10 formed on the second main surface of the n-type single crystal silicon A groove 11 is formed in a peripheral portion of the laminated body including the thin film 3. Note that the depth of the groove 11 is the same as that of the first embodiment until at least the stacked body including the n-type amorphous silicon layer 10 and the conductive thin film 3 is removed and reaches the intrinsic amorphous silicon layer 8. Anything should do.

The other configuration is exactly the same as that of the first embodiment, and the description is omitted. In the present invention,
The groove for preventing short circuit may be provided on the side of the n-type single crystal silicon substrate on which the back electrode is formed.

(Embodiment 4) FIG. 5 is a sectional view showing the structure of still another example of a photovoltaic device according to the present invention.

Referring to FIG. 5, this photovoltaic element has n
P-type amorphous silicon layer 9 is formed directly on the first main surface of type single-crystal silicon substrate 7 without an intervening intrinsic amorphous silicon layer. The other configuration is completely the same as that of the third embodiment shown in FIG. 3, and the description thereof is omitted.

The present invention can be applied to a photovoltaic element in which the intrinsic amorphous silicon layer 8 is formed only on the second main surface side of the n-type single crystal silicon substrate 7 as described above.

[0064]

[0065]

( Reference Example) FIG. 6 is a cross-sectional view showing a structure of a photovoltaic element which is a reference of the present invention.

First, as shown in FIG. 1A, a plurality of photovoltaic elements having undergone the film forming process were overlaid. next,
Laser was applied to a portion outside the side surface of the substrate from a direction orthogonal to the superposed substrate surface.

As a result, as shown in FIG. 6, the intrinsic amorphous silicon layer 8, the p-type amorphous silicon layer 9, and the n-type amorphous silicon layer 8 formed on the side surfaces of the n-type single crystal silicon substrate 7 are formed. 10 and the conductive thin film 3 are removed, and the single crystal substrate 7 is removed.
The photovoltaic element with the side surfaces exposed was obtained.

As described above, intrinsic amorphous silicon layer 8, p-type amorphous silicon layer 9, n-type amorphous silicon layer 10 and conductive thin film 3 formed on the side surface of n-type single crystal silicon substrate 7. Can also effectively prevent short-circuiting and deterioration of characteristics of the photovoltaic element due to sneaking.

The above-described processing may be performed on one photovoltaic element. In particular, according to the method of this reference example , the processing by laser irradiation is performed on a plurality of substrates at once. Therefore, improvement in mass productivity can be expected.

The photovoltaic element of this reference example is shown in FIG.
A where no film is formed on the substrate as in the conventional example shown in FIG.
Since the film is formed on the entire surface of the substrate without conversion, conversion efficiency and light confinement performance are high.

FIG. 7 is a perspective view showing a modification of the reference example . Referring to FIG. 7, in this photovoltaic element, n
At least a part of the side surface of the type single crystal silicon substrate 7 in the thickness direction is exposed by the groove 1 continuously formed so as to surround the side surface.

As described above, according to the present embodiment , it is not always necessary to expose the entire side surface of the substrate as in the embodiment shown in FIG. , The short circuit of the photovoltaic element due to the wraparound is effectively prevented.

[0074]

As described above, according to the present invention,
A photovoltaic element having improved light confinement performance due to the entire surface AR coating of the conductive thin film and improved conversion efficiency due to an increase in the effective area can be obtained.

[0075]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a manufacturing process of an example of a photovoltaic device according to the present invention.

FIG. 2 is a perspective view for explaining a formation state of a groove in the photovoltaic element shown in FIG. 1 (b).

FIG. 3 is a sectional view showing the structure of another example of the photovoltaic device according to the present invention.

FIG. 4 is a sectional view showing the structure of still another example of the photovoltaic device according to the present invention.

FIG. 5 is a sectional view showing still another example of the photovoltaic device according to the present invention.

FIG. 6 is a cross-sectional view showing the structure of a reference example of a photovoltaic element manufactured according to the present invention.

FIG. 7 is a perspective view showing a modification of the reference example .

FIG. 8 is a cross-sectional view showing a structure of an example of a conventional photovoltaic element.

[Explanation of symbols]

 Reference numerals 1, 11 grooves 3 conductive thin film 4 collector electrode 5 back electrode 7 n-type single-crystal silicon substrate 8 intrinsic amorphous silicon layer 9 p-type amorphous silicon layer 10 n-type amorphous silicon layer The same reference numerals indicate the same or corresponding parts.

Continuation of front page (56) References JP-A-4-130671 (JP, A) JP-A-7-131041 (JP, A) JP-A-54-141595 (JP, A) JP-A-63-261883 (JP) U.S. Pat. No. 4,890,059 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (2)

(57) [Claims] 1. A first main one conductivity type crystalline semiconductor substrate
Other conductors formed by wrapping around from the surface to the side of the substrate
First product composed of an electrically-conductive amorphous semiconductor layer and a conductive thin film
A layer body, and the substrate from the second main surface of the crystalline semiconductor.
Amorphous semiconductor of the same conductivity type formed by wrapping around the side
A second laminated body comprising a body layer and a conductive thin film , wherein an intrinsic property is provided between the substrate and the other conductive type amorphous semiconductor layer.
An amorphous semiconductor layer; and a first peripheral portion on a first main surface of the substrate.
A photovoltaic element, wherein a groove reaching the intrinsic amorphous semiconductor layer is formed by removing the stacked body . 2. A semiconductor device comprising : a first conductive type crystalline semiconductor substrate;
Other conductors formed by wrapping around from the surface to the side of the substrate
First product composed of an electrically-conductive amorphous semiconductor layer and a conductive thin film
A layer body, and the substrate from the second main surface of the crystalline semiconductor.
Amorphous semiconductor of the same conductivity type formed by wrapping around the side
A second laminate comprising a body layer and a conductive thin film.
A photovoltaic element, wherein an intrinsic property is provided between the substrate and the amorphous semiconductor layer of the same conductivity type.
An amorphous semiconductor layer; and a second peripheral surface on the second main surface of the substrate.
To reach the intrinsic amorphous semiconductor layer
A photovoltaic element , wherein a groove is formed .